Method for Producing an ANFO Explosive Using Ammonium Nitrate and Residual Oils and Product Thus Produced

ABSTRACT

The present invention relates to a method for producing ANFO on the basis of filtration and purification of the residual oils of a mine in a filter truck especially designed and developed for this purpose, with the aim of completely replacing the diesel fuel 2 with said residual oils that have been previously treated in order to mix same with ammonium nitrate, as well as the product resulting from said method. The aim of this invention is to use the residual oil produced in mines in large quantities, as the only combustible agent in the production of ANFO, generating cost savings by completely substituting diesel 2 and additionally eliminating the existing risk inherent in the removal of the residual oil from the mine and the negative impact that it can generate in the environment if it is not used appropriately.

TECHNICAL FIELD

The present invention relates to the field of explosives, specifically to the production of ANFO using residual oils instead of diesel 2. The present invention relates to a method for producing an explosive (ANFO) using ammonium nitrate and residual oils, as well as the product produced by means of this method.

PRIOR ART

ANFO is a high-order explosive that is very widely used in the mining industry for blasting as it is very safe and inexpensive, its components can be easily obtained, in addition to the fact that the detonation of ANFO is ultrasonic and the blast is very powerful in relation to the quantity that must be used.

It is widely used in blasting medium to soft rocky soils by introducing powder in blast holes by means of compressed air or in another form of presentation with an emulsion matrix to form heavy ANFO.

The present invention essentially consists of a mixture of ammonium nitrate and petroleum-derived fuel, the conventional production method thereof producing ANFO by mixing specific quantities of ammonium nitrate and fuel which vary according to the length of the hydrocarbon chain of the fuel used. Percentages generally range from 90% to 97% ammonium nitrate and from 3% to 10% fuel, the most common being to prepare ANFO on the basis of a mixture of 94% ammonium nitrate and 6% diesel 2. In that regard, the Peruvian Technical Standard NTP 311.278 “Explosives and blasting accessories. Ammonium nitrate for ANFO. Requirements” defines ANFO as a “product formed by the mixture of ammonium nitrate for ANFO and fuel. The nominal composition by weight defined for ANFO is: 94% ammonium nitrate and 6% diesel fuel no. 2”.

In some cases, in addition to ammonium nitrate, as part of the combustible agent for producing ANFO, diesel fuel 2 is mixed with reduced quantities of residual oil equivalent to 60% diesel 2 and 40% residual oil, reaching in some cases a maximum of 50% diesel 2 and 50% residual oil. In other words, the prior art shows that residual oils have been used in the production of ANFO but always in a smaller proportion as an additional component in the combustible agent along with diesel fuel 2.

There is an unfavorable technical opinion with respect to the use of used, recycled or residual oil in the production of ANFO because although it is widely known in the prior art that used oils have also been utilized as fuel, they have the drawbacks of reducing initiation and propagation sensitivity, detonation speed and energy yield. Due to their high viscosities, they tend to remain on the surface of the ammonium nitrate granules occupying the macropores, so the complete or partial substitution of gas oil (diesel 2 or the like) with used oils is currently not justified from the economic viewpoint due to the drawbacks posed by these products. In that regard, see http://www.monografias.com/trabajos83/explosivos-tipos-y-propiedades/explosivos-tipos-y-propiedades.shtml#ixzz2wbSuvi5l.

In the same sense, European Patent EP2069266 teaches that although residual lubricating oil from vehicles used in the mine can be used as part of a water-in-oil emulsion to produce ANFO, these oils are refractory and difficult to be absorbed into ammonium nitrate itself, so they must be diluted with diesel or with another virgin oil. It adds that when the ANFO explosive comprises, as is typically the case, 5-7% by mass of lubricating oil with respect to ammonium nitrate, no more than 2-3% of the ANFO explosive can be residual lubricating oil, the remaining 3-4% being required to be virgin oil or diesel or any other component (solvent) diluting it and allowing the absorption thereof into ammonium nitrate which is the most important oxidizing component of this explosive.

In some cases, the attempt has been made to dilute the used oil in water, creating a water-in-oil emulsion to which emulsifiers and surfactants must be added (EP2069266), but there is no prior art which has completely eliminated the use of diesel 2 or a similar hydrocarbon, being substituted only with duly filtered and purified residual oil according to the method of the present invention.

On the other hand, it can be easily seen that mines, as part of their operations, produce a large quantity of gallons of used or residual oil of different types and originating from different sources, such as engine oil, lubricating oil, etc. This oil is usually disposed of and requires certain management and handling conditions in the mine collection, removal and transfer process in order to avoid generating negative environmental impacts and to make the process safer, generating unwanted high costs.

The foregoing thereby leads to the problem of eliminating the existing risk inherent in the removal of large quantities of highly contaminating recycled oil from the mine and the possibility of taking advantage of and reusing the residual oil that will be disposed of, instead of diesel 2, to produce ANFO, in contrast to the teachings suggested in the prior art.

DETAILED DISCLOSURE OF THE INVENTION

The present invention relates to a method for producing ANFO on the basis of residual oils instead of diesel 2 based on the treatment of said residual oils by means of a prior double filtration and purification process, as well as the product resulting from said method.

The aim of this invention is to utilize the residual oil produced in mines in large quantities as the only combustible agent in the production of ANFO, generating cost savings by completely substituting diesel 2 and additionally eliminating the existing risk inherent in the removal of the residual oil from the mine and the negative impact that it can generate in the environment if it is not used appropriately.

The developed technology allows filtering 30,000 gallons of recycled oil in a mobile unit especially designed for this purpose located at the same mine which will be referred to as a filter truck that will be in charge of purifying the residual oil obtained from the collection center by means of a double filtration system, to then supply it, instead of diesel 2, to mixing trucks for the production of ANFO, so the environmental impact is minimized, the residual oil is utilized, increased safety is generated since the oil does not leak out of the mine and cost savings are achieved as diesel 2 is no longer used.

In further detail, the method of the present invention involves the implementation of the following consecutive steps:

-   -   The filter truck removing residual oil or recycled oil from the         collection center.     -   The product being introduced through a discharge hose into the         manhole of the truck where the first 1 mm filtration is         performed.     -   The residual oil being transported to the points at which the         explosive producing trucks are located.     -   The filter truck pumping and driving the residual oil so that it         goes through two 30-micron serial filters (second filtration)         and then through a gallon counter.     -   The already filtered residual oil being ejected with a swing gun         to the fuel-mixture tank of the explosive producing truck.     -   The explosive producing truck integrating the twice filtered         residual oil into ammonium nitrate to produce ANFO.

To fulfill this function, the filter truck especially developed for this process is formed by the following components:

-   -   Cistern tank: used for storing residual oil.     -   Vent valve: used for introducing oxygen into the tank for the         free flow of the residual oil, pneumatically operated.     -   Four manholes or upper access holes used for pre-filtering the         recycled oil in a 1 mm mesh for solid retention.     -   Mixer: used for mixing and circulating the recycled oil.     -   Cleaning valves: used for extracting sludge formed at the bottom         of the cistern tank as a result of the binding of particles that         went through the first filter.     -   Pump: used for suctioning the residual oil and delivering it         under pressure to the mixing truck.     -   Suction valve: used for moving the residual oil out to the pump.     -   Suction filter: up to 0.5 mm used for cleaning the residual oil.     -   Hydraulic motor: allows providing rotational movement to the         residual oil pump.     -   Comptometer: allows viewing the gallons of residual oil that are         being delivered to the mixing truck.     -   Dispensing valve: used for controlling the filling of the mixing         truck tank with residual oil.     -   Chassis: vehicle used for transferring the components for         residual oil storage and pumping.

The technical problem that is being considered is solved based on the use of the method of treating and purifying residual oils through a double filtration process which allows using same as the only combustible component in the production of ANFO, completely substituting diesel fuel 2.

This method of treating and purifying residual oils in turn requires the intervention of a filter truck especially designed and implemented for fulfilling the purposes of this method as it has storage, loading, filtering (at two different levels), mixing, pumping, cleaning, venting, suctioning, measuring and unloading mechanisms. As mentioned, this novel recycling truck is in charge of purifying residual oils through a double filtration scheme at different times during the method and pumping these residual oils, once they are suitable for said purpose, to the producing truck to be mixed with ammonium nitrate.

Since the method is largely carried out in the recycling truck, the present invention allows the implementation thereof in the mine itself without having to transfer the residual oils, mitigating environmental risks.

The product resulting from this method has the same features and properties as conventional ANFO, showing the following composition:

Ammonium nitrate 94% 100% residual oil 6% ANFO 100%

ADVANTAGES OF THIS TECHNOLOGY

This process completely replaces diesel 2 and allows utilizing residual oils for producing ANFO. Furthermore, the mobility advantage is achieved since unlike the static older technology, this technology is more flexible and dynamic as it uses a truck for oil filtration.

This technology furthermore allows eliminating the existing risk inherent in the removal of the residual oil from the mine as a result of the in situ implementation of a filter truck as an essential element allowing the use of all the residual oil in the production of ANFO for mine blasting.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a flow diagram with the steps of the method and the location in which each of them is performed.

FIG. 2 shows a drawing with the detail of the steps of the method showing the residual oil being supplied from the collection center, introduced through the manholes of the filter truck in which the first 1 mm filtration is started (a), the residual oil filter truck then transports the residual oil to the points at which the explosive producing trucks are located (b), whereas the residual oil filter truck pumps the residual oil through two 30-micron serial filters to the fuel hopper of the explosive producing truck (c) so that the explosive producing truck finally integrates the residual oil into ammonium nitrate to form ANFO (d).

FIG. 3 shows a plan view of the step of loading from the storage tanks to the filter truck.

FIG. 4 shows an elevational view of the step of loading from the storage tanks to the filter truck.

FIG. 5 shows a plan view of the unloading from the filter truck to the producing truck.

FIG. 6 shows an elevational view of the unloading from the filter truck to the producing truck.

FIG. 7 shows the general overview.

FIG. 8 shows a side elevational view of the filter truck with four manholes, each with a 1 mm filter (a), a mixer (b), a hydraulic motor (c) a cleaning valve (d) and a suction valve (e).

FIG. 9 shows a plan view of the filter truck.

FIG. 10 shows a rear elevational view of the filter truck with the pump (a), comptometer (b), suction valve (c), 30-micron dual filter (d) and swing coupling (e). 

1-3. (canceled)
 4. A method for producing ANFO on the basis of ammonium nitrate and purified residual oil, comprising a double residual oil filtrate with the following steps: The filter truck removing residual oil from the collection center The product being introduced through a discharge hose into the manholes or access holes of the truck where the first 1 mm filtration is performed The residual oil thus filtered being transported to the points at which explosive producing trucks are located The filter truck pumping and driving the residual oil through two 30-micron serial filters, in which the second filtration is performed; then the residual oil circulates through a gallon counter The already twice filtered residual oil being ejected with a swing gun to the fuel-mixture tank of the explosive mixing truck The explosive mixing truck integrating the twice filtered residual oil into ammonium nitrate.
 5. The method of claim 4, wherein the filter truck in which the steps of the method are carried out is formed by the following components: Cistern tank in which the residual oil is stored Vent valve by which the oxygen is introduced into the tank Manholes or access holes located at the top of the truck, each with the respective filters with 1 mm sieve for solid retention Mixer Cleaning valves Suctioning and delivering-under-pressure pump of the residual oil Suction valve Suction filter Hydraulic motor Viewing-of-gallons-of-residual-oil-that-are-delivered-to-the-mixing-truck comptometer Dispensing-of-controlling-the-filling-of-the-mixing-truck-tank-with-residual-oil valve Chassis on which the components are transferred.
 6. An ANFO-type explosive produced by the method of claim 4, comprising residual oil instead of diesel 2 in the combustible phase thereof having the following composition: Ammonium nitrate 92% 100% purified residual oil 8% ANFO 100% 